Air-Permeable Composite Fabric

ABSTRACT

An air-permeable composite fabric is provided. The composite fabric has an inner fabric layer, an outer fabric layer, and an intermediate vapor barrier. The vapor barrier is selected from adhesive material and an adhesive/membrane combination designed so the composite fabric has a level of air permeability to allow air flow between the first fabric layer and the second fabric layer and a variable level of water vapor diffusion resistance that decreases as air speed impinging on the composite fabric increases.

This application is a continuation of and claims the benefit of U.S.application Ser. No. 11/434,017, filed on May 15, 2006, which is acontinuation of U.S. application Ser. No. 10/650,098, filed Aug. 25,2003, now pending, which is a continuation of U.S. application Ser. No.09/378,344, filed Aug. 20, 1999, now abandoned, which claims the benefitof U.S. Provisional Application No. 60/098,254, filed Aug. 28, 1998, nowexpired. U.S. application Ser. No. 10/650,098, filed Aug. 25, 2003, nowpending, is also a continuation of U.S. Ser. No. 10/341,309, filed Jan.13, 2003, now abandoned, which is a continuation of U.S. applicationSer. No. 09/863,852, filed May 23, 2001, now abandoned, which is adivisional of U.S. application Ser. No. 09/378,344, filed Aug. 20, 1999,now abandoned. The contents of the prior applications are consideredpart of (and are incorporated by reference in) the disclosure of thisapplication.

BACKGROUND

This invention relates to a fabric material, and more particularly, to acomposite fabric having controlled wind permeability.

Conventional composite fabrics are designed to be fully wind resistant.By way of example, reference is made to U.S. Pat. Nos. 5,204,156;5,268,212; and 5,364,678, all entitled “Windproof and Water ResistantComposite Fabric With Barrier Layer,” and which describe a drapable,stretchable, windproof, water resistant and water vapor-permeablecomposite fabric. This composite fabric includes an inner fabric layer13A, an outer fabric layer 13B, and a barrier or membrane layer 17A (seeFIG. 1). The barrier or membrane layer is constructed to prevent air andwater from passing through the fabric layers. Testing has shown that theamount of air flowing through such a composite fabric is on the order orno more than 1 ft.³/ft.²/min.

The membrane or barrier of this type of prior art fabric composite istypically adhered or bonded to the fabric layers with the aid of anadhesive 18. The adhesive can be made from a polyurethane, polyester,acrylic or polyamide. Reference is made to FIG. 1, which illustrates thecomposite fabric of the prior art.

The above-described fabric composite is nonetheless less than desirable.Because such a composite fabric allows only minimal air flowtherethrough, the wearer of the fabric may not be comfortable. When aperson wearing a garment constructed with the composite fabric of theprior art performs some type of physical activity, heat is almost alwaysgenerated, even if the outside air is cold. In order to adjust for thisheat generation, the two fabric layers may be selected to have lowinsulative properties. However, this is disadvantageous, since usingsuch a fabric composite will cause the wearer to feel cold when noactivity is being performed.

Another disadvantage with prior art composite fabrics is the level ofmoisture vapor transmission. For example, a membrane made ofpolytetrafluroethylene, while having a higher moisture vaportransmission performance than a polyurethane membrane, is still notdesirable, since it cannot handle a situation where high levels ofmoisture vapor or sweat are generated. As a result, wearer discomfort isoften prevalent, due to this limitation on moisture transport.Specifically, excess moisture which could not be transported out fromthe fabric condenses next to the skin-side surface, producing a coldfeeling on the skin of the person wearing a garment made from this typeof prior art composite fabric.

Accordingly, it is desirable to provide an improved windproof, watervapor permeable fabric which eliminates the problems associated withprior art fabrics.

SUMMARY

Generally speaking, in accordance with the invention, a wind resistantand water vapor permeable composite fabric is provided. The compositefabric includes an inner fabric layer, an outer fabric layer, and anintermediate vapor barrier. The vapor barrier is selected from adhesivematerial and an adhesive/membrane combination designed so the compositefabric has a level of air permeability to allow air flow between thefirst fabric layer and the second fabric layer and a variable level ofwater vapor diffusion resistance that decreases as air speed impingingon the composite fabric increases.

The adhesive may be a continuous film which is mechanically altered bymeans of crushing, stretching and the like to enhance air permeabilityor a discontinuous film which inherently enhances air permeability. Theadhesive and/or the membrane may be applied directly to a fabric surfaceof one or both of the fabric layers or may be applied by means oftransfer coating from release paper.

In one example, the adhesive functions as a vapor barrier and isdisposed between the two fabric layers. The adhesive may be in the formof a foam. One or more rollers may be used to apply pressure to thefabric in order to selectively adjust the air permeabilitycharacteristics thereof.

In a second embodiment, the vapor barrier comprises a membrane made frompolyurethane, polyamide, polytetrafluroethylene or polyester, or acombination thereof, which is applied between the two fabric layers 15and adhered thereto with an adhesive. The fabric composite undergoesmechanical processing, such as controlled stretching, in order toachieve a desired level of air permeability.

According to one aspect of the invention, an air-permeable compositefabric comprises a first fabric layer, a second fabric layer, and anintermediate, air-permeable vapor barrier disposed between and bonded tothe first and second fabric layers. The intermediate, air-permeablebarrier layer is selected from the group consisting of: a foamedadhesive in the form of a discontinuous film, an adhesive in the form ofa continuous film mechanically altered by one of crushing andstretching, and a membrane disposed between and adhered to the firstfabric layer and the second fabric layer with an adhesive andmechanically altered by stretching. The intermediate, air-permeablevapor barrier layer has a level of air permeability to allow air flowbetween the first and second fabric layers, and the intermediate,air-permeable vapor barrier layer has a variable level of water vapordiffusion resistance that substantially decreases as air speed of movingair impinging on the fabric increases.

Preferred embodiments of this aspect of the invention may include one ormore of the following additional features. The adhesive is selected fromthe group consisting of polyurethane, acrylics, polyamides, polyestersand combinations thereof. At least one of the first and second fabriclayers is rendered hydrophilic. At least one of the first and secondfabric layers has a raised surface. The intermediate, air-permeablevapor barrier comprises an adhesive selected from the group consistingof: an adhesive in the form of a mechanically altered continuous filmand a foamed adhesive in the form of a discontinuous film. The vaporbarrier is exclusively foamed adhesive in the form of a discontinuousfilm. The intermediate, air-permeable vapor barrier comprises themembrane disposed between the first and second fabric layers and adheredthereto with an adhesive and mechanically altered by stretching, thecomposite fabric having undergone mechanical processing. The membrane ismade from a material selected from the group consisting of polyurethane,polyamide, polytetrafluoroethylene, polyester and combinations thereof.The mechanical processing comprises controlled stretching. The adhesiveis selected from the group consisting of polyurethane, acrylics,polyamides, polyesters and combinations thereof.

According to another aspect of the invention, a method of forming anair-permeable composite fabric comprising the steps of: selecting avapor barrier from the group consisting of a membrane and an adhesive,disposing the vapor barrier between a first fabric layer and a secondfabric layer in order to produce the composite fabric, and mechanicallyprocessing the composite fabric of such that the intermediate,air-permeable vapor barrier layer has a level of air permeability toallow air flow between the first fabric layer and the second fabriclayer and the intermediate, air-permeable vapor barrier layer has avariable level of water vapor diffusion resistance that decreases as airspeed impinging on the composite fabric increases.

Preferred embodiments of this aspect of the invention may include one ormore of the following additional features. The vapor barrier is amembrane, and the step of mechanical processing comprises controlledstretching of the composite fabric. The vapor barrier is an adhesive,and the step of mechanical processing comprises applying pressure to thecomposite fabric. The method comprises passing the composite fabricthrough a plurality of rollers while applying pressure. The methodcomprises passing the composite fabric through a plurality of heatedrollers while applying pressure. The method comprises passing thecomposite fabric through the rollers at variable controlled speeds.Preferably, the adhesive is foamed. The method comprises disposing theadhesive between the first fabric layer and the second fabric layer bytransfer coating using release paper. The method comprises disposing thevapor barrier between the first fabric layer and the second fabric layeras a continuous film of adhesive. The method comprises disposing thevapor barrier between the first fabric layer and the second fabric layeras a discontinuous film of adhesive. The method comprises disposing thevapor barrier between the first fabric layer and the second fabric layeras a film of adhesive using release paper. The method comprisesdisposing the vapor barrier between the first fabric layer and thesecond fabric layer by applying the adhesive directly to at least one ofthe first fabric layer and the second fabric layer.

Accordingly, it is an object of the invention to provide an improvedwindproof composite fabric, whose wind resistance may be varied.

Still another object of the invention is to provide a composite fabricwhich is water resistant.

A further object of the invention is to provide an air-permeablecomposite fabric.

Yet another object of the invention is to provide a composite fabrichaving a moisture vapor transmission rate which substantially increasesas air speed impinging on the fabric increases.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the following description.

The invention accordingly comprises the several steps and the relationof one or more steps with respect to each of the others, and the fabricpossessing the features, properties and construction of elements whichare exemplified in the following detailed disclosure, and the scope ofthe invention is indicated in the claims.

DESCRIPTION OF DRAWINGS

For a fuller understanding of the invention, reference is made to thefollowing description, taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a front view in cross-section illustrating a composite fabricof the prior art;

FIG. 2 is a front view in cross-section illustrating a composite fabricmade in accordance with the invention;

FIG. 3A is a graph which shows the change in moisture vapor transmissionas a function of air permeability in the inventive composite fabric;

FIG. 3B is a graph showing the change in air permeability as a functionof thermal resistance in the inventive composite fabric;

FIG. 4A is a front view in cross-section showing formation of a secondembodiment of the composite fabric of the invention;

FIG. 4B shows the effects of controlled stretching on the compositefabric depicted in FIG. 4A;

FIG. 5 is a front view in cross-section showing the formation of a thirdembodiment of the inventive composite fabric;

FIG. 6 is a front elevational view in cross-section showing theformation of a fourth embodiment of the inventive composite fabric; and

FIG. 7 is a graph showing the relationship of water vapor resistance asa function of wind speed impinging on the inventive fabric as comparedto prior art fabrics.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring first to FIG. 2, a first embodiment of the inventive compositefabric, generally indicated at 11, is shown. Fabric 11 comprises firstand second fabric layers 13 and 15, and a barrier 17 disposedtherebetween. Fabric 11 has variable water vapor permeability, asdiscussed below. In this embodiment, the barrier 17 consists of anadhesive material. Adhesive 17 may, in one form, be applied by means oftransfer coating from release paper at between 0.25 oz/yd² and 2.5oz/yd². Each of layers 13 and 15 may be treated or modified, asdescribed in U.S. Pat. Nos. 5,204,156; 5,268,212; and 5,364,678,including rendering the layers hydrophilic, providing the layers with araised surface, treating the layers to be water repellant, etc.

Fabric 11 is formed to any specific controlled wind resistantperformance level, as discussed below. As shown, air which impinges uponfabric 11 is partially deflected away from the barrier 17 and partiallypenetrates as well through the barrier 17.

In the absence of moving air, water vapor/moisture from the skin canonly transfer through the fabric by means of an absorption/adsorptionphenomenon leading to excess heat buildup and moisture. When fabricallows some air to pass through the barrier, it helps in transferringhigh moisture levels and thus make the wearer more comfortable.

Importantly, as wind speed increases, more air flows through thebarrier, allowing more vapor to be dissipated. Thus, the compositefabric of the invention has a relatively high water vapor permeabilityin moving air, and has substantially reduced resistance to vaporpermeability with an increase in air flow. The reduction in windresistance or increase in air permeability will not cause anysignificant loss of the thermal insulative properties, as shown in thegraphs of FIGS. 3A and 3B now discussed, because the actual amount ofair penetrating the barrier is minimal.

The graph of FIG. 3A illustrates that for any increase in airpermeability of the inventive fabric, there is a corresponding decreasein evaporation pressure resistance. The graph of FIG. 3B shows that forany increase in air permeability of the inventive fabric, there will bea corresponding decrease in thermal resistance of the composite fabric.As can be appreciated from reviewing the graphs, there is a substantialdifference between the magnitude of change in evaporation pressureresistance and thermal resistance. Evaporation pressure resistance dropsfar more rapidly than thermal resistance for the same amount of changein air permeability of the composite fabric. Thus, when there is a smallincrease in air permeability of the composite fabric, the evaporativepressure resistance reduces significantly. As evaporation pressureresistance decreases, more moisture can be transported across thecomposite fabric, and thus, the loss in thermal resistance which definesthe warmth of the fabric is not affected significantly.

FIG. 4A describes a second embodiment of the inventive composite fabric,which is generally indicated at 21. Composite fabric 21 includes firstand second fabric layers 23 and 25, a barrier that in this case is anintermediate membrane 27, and an adhesive 29 on both sides of membrane27 for adhering membrane 27 to fabric layers 23 and 25. Adhesive 29 may,in one form, be applied by means of transfer coating from release paperat a thickness of between 0.25 oz/yd² and 2.5 oz/yd². Membrane 27 ismade from polyurethane, polytetrafluroethyelene or polyester. Membrane27 may be applied by means of transfer coating from release paper at athickness of between 0.0001 in. and 0.010 in., or directly on the fabricsurfaces at a thickness of between 0.0003 in. and 0.010 in.

As shown in FIG. 4B, composite fabric 21 having a width, W, is subjectedto controlled stretching to produce a composite having a width, W′, witha desired specific level of air permeability.

Referring now to FIG. 5, a third embodiment of the inventive compositefabric is shown and generally indicated at 31. Composite fabric 31includes fabric layers 33 and 35, and a barrier consisting of anintermediate adhesive 37. The adhesive is chosen from a polyurethane,polyester, acrylic and polyamide. Here, adhesive 37 is applied as a foamat between about 0.3 oz/yd² and 10 oz/yd². The foam density (mixing airwith adhesive) and the amount of adhesive applied are selected dependingon the desired air permeability of the composite. Composite fabric 31 isprepared by first applying foam adhesive 37 on one of the opposedsurfaces of fabric layers 33 and 35. Once applied, the other fabriclayer is put over the adhesive in order to produce the inventive fabriccomposite. Composite 31 is then mechanically processed by means of apair of rollers 39, which apply pressure thereto in an amount betweenabout 10 lbs./in.² and 150 lbs/in.² in order to produce a compositehaving a specific level of air permeability.

Referring now to FIG. 6, a further embodiment of the inventive compositefabric is shown. Composite fabric 41 comprises fabric layers 43 and 45and a barrier formed of an intermediate adhesive 47. Air permeability iscontrolled by applying the adhesive on the fabric and then using sometype of mechanical processing, such as treatment with rollers 19, inorder to create the desired levels of air permeability.

Still referring to FIG. 6, adhesive 47 may, in one form, be applied bymeans of a release paper. The adhesive is first placed on the releasepaper at between about 0.25 oz./yd.² and 2.5 oz./yd.², after which oneof the fabric layers is put on top thereof in order for bonding tooccur. Then, the release paper is stripped from the fabric and thesecond fabric layer is applied to the other side of the adhesive. Thecomposite then undergoes mechanical processing by rollers 49 (which maybe heated to a temperature of between about 100° F. and 375° F.), whichapply pressure to the composite fabric. As can be appreciated, changingany mechanical parameter (roller temperature, pressure applied, andspeed of the fabric through the rollers) helps change the airpermeability characteristics of the composite fabric.

Alternatively, and still referring to FIG. 6, adhesive 47 may be applieddirectly to one of fabric layers 43 and 45 (at 0.25 oz./yd.² to 2.5oz./yd.²) without the use of release paper. As before, the compositefabric will undergo mechanical processing in order to achieve a desiredair permeability performance.

FIG. 7 describes the advantages of the present invention over the priorart. In this figure, lines A and B show the water vapor diffusionresistance for two prior art fabrics (GORE WINDSTOPPER® fabric usingGORE-TEX® PTFE membrane from WL. Gore & Associates, Inc. (Newark, Del.)and ET551 laminate with PTFE from Tetratec Corporation (Feasterville,Pa.)). As seen in FIG. 7, the diffusion resistance for these prior artfabrics is substantially constant. However, in the materials identifiedby lines C, D, E and F, corresponding respectively to various airpermeability level samples (high to low), the vapor diffusion resistancedecreases dramatically with increased wind speed through the fabric.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, and,since certain changes may be made in carrying out the above method andin the fabric construction set forth without departing from the spiritand scope of the invention, it is intended that all matter contained inthe above description and shown in the drawings shall be interpreted asmerely illustrative, and should not be considered limiting.

The following claims are intended to cover all of the generic andspecific features of the invention described herein, and all statementsof the scope of the invention which might be said to fall therebetween.

1. An air-permeable composite fabric comprising: a first fabric layer; asecond fabric layer; and an intermediate, air-permeable vapor barrierdisposed between and bonded to said first fabric layer and said secondfabric layer, wherein: said intermediate, air-permeable barrier layer isa continuous film mechanically altered by crushing the composite fabricbetween a plurality of rollers; said intermediate, air-permeable vaporbarrier layer has a level of air permeability to allow air flow betweensaid first fabric layer and said second fabric layer, and saidintermediate, air-permeable vapor barrier layer has a variable level ofwater vapor diffusion resistance that substantially decreases as airspeed of moving air impinging on said composite fabric increases.
 2. Theair-permeable composite fabric of claim 1, wherein said membrane is madefrom a material selected from the group consisting of polyurethane,polyamide, polytetrafluoroethylene, polyester and combinations thereof.3. The air-permeable composite fabric of claim 1, wherein saidintermediate, air-permeable barrier layer is a continuous filmmechanically altered by crushing the composite fabric between aplurality of rollers that are heated.
 4. The air-permeable compositefabric of claim 3, wherein said plurality of rollers are heated to atemperature of between about 100° F. and 375° F.
 5. The air-permeablecomposite fabric of claim 1, wherein at least one of said first fabriclayer and said second fabric layer has a raised surface.
 6. Theair-permeable composite fabric of claim 1, wherein said intermediate,air-permeable vapor barrier is adhered to said first fabric layer andsaid second fabric layer with an adhesive.
 7. The air-permeablecomposite fabric of claim 6, wherein said adhesive is selected from thegroup consisting of polyurethane, acrylics, polyamides, polyesters andcombinations thereof.